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问题: 求极限



lim(3x+2/3x-4)的2x+5次方
x趋无穷

解答:

lim(3x+2/3x-4)的2x+5次方
=lim(3x+2/3x-4)^(2x+5)
=lim[(1+2/(3x))/(1-4/(3x)]^(2x+5)
=lim{[1+2/(3x)]^(2x+5)}/{[1-4/(3x)]^(2x+5)}
=lim{[1+2/(3x)]^{(3x/2)*2(2x+5)/(3x)}}
/{[1-4/(3x)]^(-3x/4)*[-4(2x+5)/(3x)}}
==lim{[1+2/(3x)]^(3x/2)}^{2(2x+5)/(3x)}}
/{[1-4/(3x)]^(-3x/4)}^[-4(2x+5)/(3x)}}
=e^(4/3)/e^(-8/3)
=e^4